Turbidimeters have been known and used for decades for nephelometric measurement of color, turbidity, light absorbance and transmittance of liquids. Typically, a sample of the liquid to be tested is placed in a transparent glass cell which is then inserted into the instrument. A light beam is then directed through the cell and appropriate measurements are taken of the light scattering, absorbance and transmittance.
The greatest source of error (accuracy and non-reproducibility) in laboratory nephelometric measurement of sample turbidity (clarity) is sample cell variability and condition. Also, with single, individual sample cells, measurements of samples under dynamic flow conditions are not possible. Another source of error results from using different sample cells which may have different optical characteristics. Yet another source of error results from inherent cell flaws and scratches in the cell glass.
Although there have been previously proposed flow-through cell designs for use with a turbidimeter, such designs do not easily accommodate the need to measure a sample under either static or dynamic conditions. Rather, such designs are intended to operate either in a static condition or dynamic condition but not in both. Further, prior designs did not provide assurance that the system was completely purged of liquid sample, trapped or entrained air bubbles, and solid materials which are found in the sample.
Cells that have both the inlet and outlet in the top can collect heavy particles (which are not able to exit the cell). Cells that have both the inlet and outlet at the bottom collect bubbles and buoyant particles. Cells that have the inlet in the bottom and the outlet in the top collect heavy particles.
Some cells are extremely difficult to clean, and cleaning them consists of unscrewing barb fittings and disassembling "windows" in the cell. Thus, some cells require considerable amounts of maintenance.
The prior cells are not capable of siphoning the volume of sample out of them. Therefore, they require large amounts of DI water to purge or they require large amounts of DI water to purge the previous sample. Also, some cells have larger dead volumes and thus have slow response time.
Previous cell systems do not have the capability to be automatically (electronically) controlled by the instrument.
There has not heretofore been provided a flow cell system for a turbidimeter having the advantages and features provided by the present invention.